Essential hypertension (EH) is a major health concern in the United States; it is especially prevalent in the black population. Attempts to account for the racial difference in EH have tried to apply the risk factor approach, in which variables such as obesity, smoking, alcohol intake, sedentary lifestyle, dietary history, and heredity are presumed to relate directly to this difference. It is generally agreed that the reduction of risk factors is the major goal of any program for the prevention of EH. An increasing body of evidence supports the concept that cardiovascular reactivity is a marker, and possibly an important risk factor in its own right, in the evolution of EH. To date, there are limited data which address differences in cardiovascular reactivity to psychologic and/or physical challenge between blacks and whites. We have demonstrated that cardiovascular reactivity to physical and psychologic stress does differ between groups of healthy black children and white children. The objectives of this study are to assess in a 2(race of subject) x 2(sex of subject) x 3(parental hypertension status) design the following: 1) differences in responses to stressful stimuli: psychologic, physical, and "everyday life," 2) effects of the components of the Type A/B behavior dimension, 3) relation of cardiovascular reactivity to metabolic, enzymatic, and dietary measurements, including plasma renin, Ca++, Na+ intake and excretion, and erythrocyte Na+ K+-ATPase, 4) effects of dietary loading of Na+, K+, Ca++, NaCl, and placebo upon the reactivity, metabolic, and enzymatic measurements. The results of this study may justify the development of new diagnostic procedures for the simple, non-invasive assessment of potentially important risk factors. These new procedures could be incorporated into a program of preventive cardiology screening and possibly prospective intervention studies.